<html>
<head>
<style>
div {
  border: 10px red solid;
  width: 80px;
  height: 80px;
  margin-top: 10px;
}
#test1, #test2 {
  margin-top: -100px;
  border-color: black;
}
#reference1 {
  border-radius: 0px 0px 0px 0px;
}
#test1 {
  border-radius: 30px -150px 30px 30px;
}
#reference2 {
  border-radius: 0px 30px 0px 0px;
}
#test2 {
  border-top-left-radius: -120px;
  border-top-right-radius: 30px;
}
</style>
</head>
<body>
<div id="reference1"></div>
<div id="test1"></div>
<div id="reference2"></div>
<div id="test2"></div>
</p>
</body>
</html>
